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Abstract Small scale hybrid power systems gain popularity around the world as a viable way of reducing power generation environmental impact, reducing energy cost and increasing power supply reliability. Hybrid systems which are based on variable renewable sources usually utilize the effect of resources temporal, and to a smaller extent, spatial complementarity. Although there is already an extensive body of literature investigating the concept of resources complementarity, they rarely addressed the impact of complementarity on the reliability of a given hybrid system. In this paper we simulate the operation of wind and solar hybrid energy system (with and without battery) for evenly distributed 86 locations in Poland over the period 2010–2016 based on 15 min’ time step data. We analyze the impact of resources complementarity (on various time scales: 15 min, hourly and monthly) on the system reliability. To remove the capacity factor (resources availability depends on location) on the results, we select the installed capacity in wind and solar sources in such a way that on an annual scale they generate evenly 50% of the observed demand (which is assumed to be constant = 1 kW). We investigate the impact on complementarity in the system reliability for hybrids with and without energy storage. The second part of the paper deals with the problem of simulating the system reliability (in terms of Loss of Load Parameter) based on multiple linear regression and artificial neural networks. The results indicate that both temporal complementarity (expressed as coefficient of correlation) and storage capacity has non-linear impact on the hybrid system capacity to cover the load. Generated relations between mentioned factors show how complementarity indices may be used to size the solar-wind hybrids. The follow up studies should concentrate on analyzing the operation of hybrids utilizing more than two energy sources and juxtaposing complementarity based reliability assessment with other methods. Highlights • Resources temporal complementarity has a non-linear impact on system reliability. • Neural networks efficiently model the reliability based on resources and hybrid parameters. • Complementarity indices can be used to improve the sizing methods of hybrid systems. [ABSTRACT FROM AUTHOR]

Brazil has an energy system with a hydrothermal characteristic that interconnects consumers and generators covering 98% of the demand for energy supplies. Most of the plants are concentrated in the southeast region, where the largest consumers and the largest population concentration are located. The expansion of this system, considering the hydroelectric contributions, will occur exploring the potentials located in the Amazon region. This analysis paper shows that the variations imposed by climate changes on some climatological variables create significant uncertainties about the power generation forecasts of the hydroelectric power plants to be installed in the Amazon, thus compromising the financial economic feasibility of these enterprises and also possibly compromising the expansion plans of the Brazilian energy system. The methodological approach uses information from various climate change scenarios and compares those with historical hydrological patterns and generation information. By exploring the characteristics of a large-scale hydrothermal system with high dependence on water resources, this paper provides valuable insights on how energy policy would address hydroelectric vulnerabilities and climate change. This analysis is focused on the Brazilian case but reveals important issues related to systems with hydro thermal characteristics. [ABSTRACT FROM AUTHOR]

Hydropower with water accumulation is an interesting option to consider in hybrid systems, because it helps dealing with the intermittence characteristics of renewable energy resources. The software HOMER (version Legacy) is extensively used in research works related to these systems, but it does not include a specific option for modelling hydro with reservoir. This paper describes a method for modelling a hydropower plant with reservoir with HOMER by adapting an existing procedure used for modelling pumped storage. An example with two scenarios in southern Brazil is presented for illustrating and validating the method explained in this paper. The results validate the method by showing a direct correspondence between an equivalent battery and the reservoir. The refill of the reservoir, its power output as a function of the flow rate and installed hydropower capacity are effectively simulated, indicating an adequate representation of a hydropower plant with reservoir is possible with HOMER. [ABSTRACT FROM AUTHOR]

In recent years, renewable resources have become an important alternative to increase the capacity of power generation. Among the resources available, the energy in the oceans have attracted more interest and experiencing a period of strong development. Wave energy is the one that is currently closest to reach a stage of technical and economic maturity. In this process, computational tools to facilitate evaluation of the feasibility of power systems including ocean wave power plants are critical. This paper presents the use of software Homer, version Legacy, for evaluation of technical and economic feasibility of hybrid energy systems including contribution of wave energy. Homer is a software designed for the optimization of micro power systems that has a very broad spectrum of applications. A case study in southern Brazil is presented, studying the inclusion of an ocean wave power plant in a wind biodiesel hybrid system and showing the functionality of Homer for this purpose. [ABSTRACT FROM AUTHOR]

Most renewable energy technologies suffer from an intermittent characteristic due to the diurnal and seasonal patterns of the natural resources needed for power generation; therefore, a complementary energy storage system must be considered. The pumped hydropower plant is a suitable alternative to consider as an energy storage device for hybrid systems. The hybrid optimization model for electric renewables (HOMER) optimization model is widely used around the globe for designing, comparing, or evaluating the performance of hybrid power systems, but it does not include an explicit component to model a pumped hydropower facility. This paper describes a method for representing a pumped hydropower plant by creating an equivalent battery in HOMER, and the procedure was accompanied by a detailed example. An additional example of a wind-hydro hybrid power system with controlled parameters is presented to validate the method. The results support that the procedure explained in this paper adequately represents the pumped hydropower plant as an equivalent battery. [ABSTRACT FROM AUTHOR]

The ocean wave energy resource is a real alternative to supply part of the energy demand in various countries, since some locations have a remarkable capacity to generate electricity. The objective of this study is to evaluate the energy resource of ocean waves in the coast of Rio Grande do Sul, the southern state of Brazil. This note presents the first results. The wave data used were collected in the sea area near the Port of Rio Grande during the years 1996 to 1999, amounting to sixteen months of monitoring. The data set was treated and grouped resulting information monthly, seasonal and annual basis. The annual average was found to be 8.6 kW per meter of wave front, reaching 14.0 kW per meter for the month of May and 4.0 kW per meter for the month of January. The results indicate good perspectives in obtaining power supplies. [ABSTRACT FROM AUTHOR]

The Negro and Solimoes rivers join in front of the Brazilian city of Manaus to form the Amazon River. This "meeting of the waters" is a natural phenomenon of great aesthetic beauty that has been the focus of attention of researchers all over the world in various scientific fields. The waters of the Negro are darker and warmer, while the waters of the Solimoes are lighter and cooler. These waters have very different characteristics and remain without mixing, flowing side by side for several miles. Some reports indicate a temperature gradient between the waters of the order of 6°C, which can be used in conjunction with very high flow rates delivered by the two rivers, with a heat engine operating on a thermodynamic cycle to provide electricity. This review paper identifies this energy resource and presents a preliminary assessment of the potential for power generation. A realistic assessment of the potential points to an available power of about 1GW. It is clear that further studies are needed to accurately assess the available thermal gradient and its variation over time, to move forward in the design of the power converter, and to establish an appropriate location for a power plant. [ABSTRACT FROM AUTHOR]

The ocean can be a strategic alternative for obtaining energy supplies, both from ocean waves as from sea currents and tides. Among these features, the power generation projects based on ocean currents are still under development. Generating energy from ocean can have great impact on the Brazilian energy grid, since Brazil has a vast coastline, with more than 9,000 km long, with potential for generating energy from ocean currents not fully estimated. This article presents a preliminary determination of the energy potential for power generation from ocean currents along the coast of Rio Grande do Sul, the southernmost state of Brazil, and also presents notes that contribute to the characterization of the system of ocean currents in the region. The data used were obtained in two areas near Tramandaí, allowing the determination of velocities and directions of the currents on a seasonal basis. The maximum speeds obtained rarely exceed 0.750 m/s, while the average speeds do not exceed 0.200 m/s. A relationship with the prevailing winds in the region was identified. Unfortunately, the results do not allow optimism about the power generation from ocean currents on the southern coast of Brazil, at least over the continental shelf. [ABSTRACT FROM AUTHOR]

Abstract: The combination of hydroelectric and photovoltaic sources of energy in a generation system may seem unfeasible due to the still quite high costs of the photovoltaic plants. However in the next few decades, significant reductions in those costs are to be expected. Moreover, this combination may reduce the cost of plants implemented in low hydroelectric potential sites for which main system interconnection costs prove prohibitive. The study of hybrid hydro-PV generating plants allows the evaluation of the use of water reservoirs and battery banks as alternatives for energy storage within a system. It also allows the evaluation of the advantages of generation from complementary energy sources. The objectives of this paper is to propose the concept of a theoretical performance limit for the plants and propose a method for the determination of this performance limit using computer simulations with idealized energy availability functions. Using this method, the effect of different degrees of complementarity in time of the energy resources on the performance of hydro PV plants is studied. It has been observed that, as expected, the smallest failure indexes measuring the energy supply to the consumers are associated to the best complementarity in time indexes. The results of the simulations led to the synthesis of failure index curves, as functions of the different degrees of complementarity in time, with data obtained solely with the utilization of idealized functions describing the energy availabilities, as proposed in this work. The results so obtained are a preliminary set treating the influence of the complementarity characteristics on the performance of hybrid plants based on hydro and solar energies and show how the complementarity characteristics may be used to design hybrid power generation systems showing improved efficiency. The subsequent research work shall proceed to at least two different phases. In the first one, the method exposed in the present work shall be applied to real data and compared to the operation of existing hydro PV plants. In the second phase the obtained relations of the performance of the system to the different degrees of complementarity shall be confronted with design parameters of hydroelectric-photovoltaic plants based on complementary resources. [Copyright &y& Elsevier]

Abstract: The power plants based on renewable sources face various acceptance difficulties mainly due to high initial costs and low overall efficiencies. A way to improve performance of these systems is to utilize more than one type of source of energy chosen to provide some degree of complementarity. An interesting, albeit improbable, combination is obtained using hydroelectric and photovoltaic energy, taking advantage of the complementarity between these two types of sources coupled to reservoir and/or battery storage. This paper discusses energy complementarity in time and proposes a numerical dimensionless index, evaluating this energy complementarity between two types of energy sources, in the same or in different locations, or between two sources of the same type in different locations. In the end, the results of the application of this index to the solar and water availabilities over the state of Rio Grande do Sul, in southern Brazil, is presented in the form of maps. [Copyright &y& Elsevier]

Hybrid energy systems have higher initial costs than systems that are based on only one renewable resource, but allow for the fulfillment of the demands of consumer loads with lower values for the cost of energy. The possible complementarity between the resources used can contribute to a better use of the available energy. On a large scale, complementarity between power plants can serve as a tool for the management of energy resources. A complete evaluation of complementarity needs to consider three components: time complementarity, energy complementarity, and complementarity between amplitudes of variation. Complementarity can also be assessed between energy resources in one place (which may be termed temporal complementarity) and between resources at different sites (termed spatial complementarity). This paper proposes a method for quantifying spatial complementarity over time and for its expression through maps. The method suggests the establishment of a hexagonal network of cells and the determination of complementary roses for each cell that contains power plants. This article also applies the method proposed to some hydroelectric plants and wind farms in the State of Rio Grande do Sul, in southern Brazil, and present the map of spatial complementarity in time obtained. [ABSTRACT FROM AUTHOR]

The aim of this work is to present a quantitative evaluation of the benefits of applying the Single-Minute Exchange of Die (SMED) implemented in a shoe mold company. Based on the application of this methodology, we noticed that real gains were obtained with very little financial investment. The improvements observed in the sector were the reduction of set-up time by 60%, with an average set-up time of approximately 7 min, and an increase in the productive capacity of the sector by around 3%. There was a reduction in the incidence of errors in the machined parts due to the standardization of the processes performed by the operators. Among the advantages presented with the new system are reduced material exchange time, reduced time spent fine-tuning, less chance of errors during exchanges, improved product quality, greater reliability with respect to reduction of dissociation stocks and the flexibilization of the production system. [ABSTRACT FROM AUTHOR]

Because of the maturity of its technology, small scale hydropower generation is one of the main energy sources to be considered to provide electricity to areas far from the national grid. Very often, because of the economic limitations of the communities that can be supplied with electricity, these projects are unappealing from the entrepreneur's point of view; however, they can have such a great positive impact on the life of these communities, with little impact on the environment, that they may well justify subsidies for their construction. This paper describes a mathematical model that combines multicriteria analysis and a knapsack problem formulation for optimizing the distribution of limited financial resources among several options available of hydropower projects with a stochastic behavior in their initial cost. The test data were obtained mainly from 14 prefeasibility studies of sites in rural Nicaragua with potential for small hydropower. Five scenarios are presented, assessing the impact of multicriteria and different subsidy conditions or economic efficiency requirements. The results indicate that the presented method is suitable to be used for an efficient distribution of limited monetary resources for funding small hydropower projects, and, therefore, can be a useful tool in decision making process. The proposed method can be adapted for application to projects based on other forms of renewable energy, and can also be adapted for prioritization of projects based on different energy resources. [ABSTRACT FROM AUTHOR]

The use of renewable resources for power supply in family homes has passed the stage of utopia to became a reality, with limits set by technical and economic parameters. This paper presents the results of a project originated from the initiative of a middle-class family to achieve energy independence at home. The starting point was the concept of home with "zero energy" in which the total energy available is equal to the energy consumed. The solution devised to meet the energy demand of the residence in question is a PV wind diesel hybrid system connected to the grid, with the possibility of energy storage in batteries and in the form of heating water and the environment of the house. As a restriction, the family requested that the system would represent little impact to the lifestyle and landscape. This paper aims to assess the consequences of reductions in the cost of the PV modules on the optimization space, as conceived by the software Homer. The results show that for this system, a 50% reduction in the cost of PV modules allows all viable solutions including PV modules. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this research was to implement new inventory management in a footwear company through the analysis of indicators obtained from inventory data collection. Design/methodology/approach: The ABC analysis methods, demand forecasting, safety stock, reorder point, and economic order quantity were applied. The items in inventory were classified by order of economic importance through ABC analysis, and the proposed indicators were analyzed to determine the moment the inventory replenishment should be carried out as well as the purchase lot size for each item. The research also investigated the behavior of the demand and pointed out the demand forecasting method that came closest to reality. Findings: The study presents a method of implementing inventory management based on indicators derived from the application of ABC curve methods, demand forecasting, safety stock, re-fulfillment point, and economic purchased lot. It also indicates how the ABC classification of stocks can check the most representative materials in stock. The study also highlights that the rejection of modifications can be surpassed by obtaining favorable results. Research limitations/implications: The inventory management applied in this work is based on indicators that resulted in two primary data that defined the size of the purchased lot to be ordered and the amount of material needed. Practical implications: The methods of ABC analysis, demand forecasting, safety stock, reorder point, and economic order quantity were applied. The items in inventory were classified by order of economic importance through ABC analysis, and the proposed indicators were analyzed to determine the moment the inventory replenishment should be carried out as well as the purchase lot size for each item. The research also explored the behavior of the demand and pointed out the demand forecasting method that came closest to reality. Originality/value: In this study, a method applied is presented, highlighting the methodological application's importance for inventory management implementation. The study contributes to the encouragement and adoption of methodologies to improve analysis and inventory management in companies. [ABSTRACT FROM AUTHOR]

Renewable energies are deployed worldwide to mitigate climate change and push power systems towards sustainability. Nevertheless, the weather-dependent nature and variability of renewable energy sources often hinders their integration to national grids. The combination of different sources to profit from their beneficial complementarity has often been proposed as a partial solution to overcome these issues. This paper introduces a novel method for quantifying total temporal energetic complementarity between three different variable renewable sources, based on well-known mathematical techniques: correlation coefficients and compromise programming. It has the major advantage of allowing the simultaneous assessment of partial and total complementarity, as well as allowing for a linear assessment of complementarity. The method is employed to study the complementarity of wind, solar and hydropower generation on different temporal scales in a region of Poland. Results show that timescale selection has a determinant impact on the estimated value of the total temporal complementarity index. • A method for simultaneous evaluation of partial and total energetic complementarity. • Method combines known metrics: compromise programming and correlations. • Timescale has a direct impact on the value of the complementarity index. [ABSTRACT FROM AUTHOR]

In this work, an estimate of the emissions of volatile organic vapors emitted at a gasoline loading terminal is presented, in the absence of a vapor recovery unit. The estimation of the emissions is evaluated by the application of the General Law of Ideal Gases, using data measured in situations of fuel loading. A total of 3800 tank truck compartment samples were collected, totaling a loaded volume of 33 161 838 liters of gasoline for about 282 hours of operation in 21 days, or in three operating weeks. The results obtained provided a first estimate of the reduction of the environmental impact, evaluated by the reduction of the mass of evaporated gasoline and the registration in a database, for the execution of future projects. [ABSTRACT FROM AUTHOR]